I have left facebook, and I am on MeWe, I run a Christian farming group there. But there is also a seed trading group there ->
Seed Traders.
https://mewe.com/join/seedtraders
I take volunteer plants I have and then I visit friends in my area and I swap plants. I have been working hard on using my aquaponic system / grow towers to multiply plants so I have more to trade and swap with others. This barter system has worked great for me and them as they get plants they want, and I get barter items I want.
I had several extra seed trays I took over to a friend, and they told me they were just about to order seed trays, and the ones I brought were exactly what they needed. It does help to focus on plants that people want, and to encourage volunteers by spreading seed all over.
Building communities is the way to go. Most people do not want to garden, but that is fine I will trade food for tools, or $, or etc.